A conventional slip torque wrench mainly has a tubular body. One end of the tubular body is provided with a driving head, and the other end of the tubular body is provided with a grip. Wherein, the driving head has a rotatable ratchet member. The interior of the tubular body is provided with a press member and an elastic member arranged sequentially in a direction from the driving head toward the grip. Thereby, when the user operates the slip type torque wrench to tighten a workpiece, the press member is elastically pushed by the elastic member for the press member to abut against the ratchet member, allowing the ratchet member to drive the workpiece to rotate. When the torque applied to the workpiece is greater than the elastic force of the elastic member, the ratchet member is instantaneously slipped and detached from the press member to generate an idling for outputting a constant torque.
However, since the press member of the conventional slip type torque wrench is simply placed in the tubular body, in actual operation, at the moment when the ratchet member is disengaged from the press member, the press member is likely to generate vibrations, resulting in that the output torque of the slip type torque wrench is unstable. Thus, the accuracy of the output torque is affected greatly. Moreover, the conventional slip type torque wrench doesn't have a window to display the current set torque value. Because the driving head of the conventional slip type torque wrench is coupled to the tubular body in a screwing manner, it is difficult to ensure the relative position between the driving head and the tubular body when locked. After locked, the position of the window is often not able to aim at the predetermined position. Accordingly, the inventor of the present invention has devoted himself based on his many years of practical experiences to solve these problems.